Computational study of room scattering influence in the THOR BNCT treatment room

BNCT dosimetry has often employed heavy Monte Carlo calculations for the beam characterization and the dose determination. However, these calculations commonly ignored the scattering influence between the radiations and the room structure materials in order to facilitate the calculation speed. The aim of this article attempts to explore how the room scattering affects the physical quantities such as the capture reaction rate and the gamma-ray dose rate under in-phantom and free-air conditions in the THOR BNCT treatment room. The geometry and structure materials of the treatment room were simulated in detail. The capture reaction rates per atom, as well as the gamma-ray dose rate were calculated in various sizes of phantoms and in the free-air condition. Results of this study showed that the room scattering has significant influence on the physical quantities, whether in small phantoms or in the free-air condition. This paper may be of importance in explaining the discrepancies between measurements and calculations in the BNCT dosimetry using small phantoms, in addition to provide a useful consideration with a better understanding of how the room scattering influence acts in a BNCT facility.